Coffee oil

ABSTRACT

A process for improving coffee oil characterised in that the coffee oil is contacted, under conditions of agitation, with a solution of a strong mineral acid in a monohydric aliphatic alcohol containing from 1 to 3 carbon atoms and separating the oil layer from the alcohol layer.

The present invention relates to a process for improving coffee oil,more particularly for the deterpenisation thereof.

Green coffee beans contain approximately 10-15% coffee oil and when usedfor the preparation of a soluble coffee the beans are roasted, ground,and then extracted with hot water. The soluble solids pass into theextraction liquid which is then steam distilled and dried to yield asoluble coffee powder. Most of the coffee oil stays with the spentgrounds from which it can be collected and used in the form of anemulsion with coffee aroma to aromatize soluble coffee by spraying on tothe soluble coffee powder so preserving or restoring the pleasantcharacteristic odour of roast coffee.

However coffee oil contains certain ingredients such as terpenes anexample of which is cafestol, free fatty acids and unsaponifiables whichrender it unsuitable for use as an edible vegetable oil. We have foundthat by a very mild treatment of coffee oil, a sufficient quantity ofthese ingredients can be extracted so that the treated oil falls withinthe standards laid down for edible vegetable oils. (Codex alimentariusstandards: General Standard for edible oils and fats CAC/RS 19-1969).The treated coffee oil, in the meantime, retains its suitability foraromatizing soluble coffee powder.

According to the present invention there is provided a process forimproving coffee oil characterised in that the coffee oil is contacted,under conditions of agitation, with a solution of a strong mineral acidin a monohydric aliphatic alcohol containing from 1 to 3 carbon atomsand separating the oil layer from the alcohol layer.

The formation of a deep blue green colouration indicates that extractionof terpenes is taking place. As the alcohol acts at the same time as anextraction solvent for other polar lipidic components, free fatty acidsand unsaponifiables are removed also. The process of the inventiontherefore not only deterpenises the coffee oil but also refines it.

The presence of water decreases the rate of extraction, the fastestrates being obtained in the presence of less than 1% and especially lessthan 0.5% by weight of water, based on the weight of the solution. Inthe presence of more than 20% by weight of water, no extraction takesplace at all.

Any strong mineral acid may be used in the process, for example nitricacid or hydrochloric acid. However sulphuric acid is particularlypreferred. The concentration of the acid in the alcohol may vary from0.1 to 2% but is preferably from 0.25 to 1.5% on a weight/volume basis.The rate of the extraction increases as the proportion of acid to oilincreases. Preferably the proportion of acid to oil is from 2.5 to 15parts and optimally from 5 to 10 parts by weight per 100 parts by weightof oil.

Of the alcohol solvents methanol is the most suitable because the oil isonly slightly soluble in it and therefore the deep blue greencolouration of the methanol layer is quite distinct from the coffee oillayer which is generally only slightly discoloured.

While ethanol is comparable to methanol, it has the disadvantage that itis somewhat hygroscopic and the technical grade contains a certainamount of water. The coffee oil is quite soluble in isopropanol at roomtemperature and therefore the yield is low and the oil is deep colouredand viscous: however, the rate of extraction is quite rapid.

The solubility in isopropanol may be decreased by adding water, forexample in an amount up to 20% by weight based on the weight of themixture. Although the rate of extraction is decreased and the processtakes longer the yield is much improved. However if the time of contactis more than 4 hours the coffee oil tends to esterify and goes intosolution.

The rate of the extraction decreases with increasing concentration ofoil in the alcohol. The concentration is conveniently from 5 to 20 partsand optimally from 7.5 to 12.5 parts by weight per 100 parts by volumeof alcohol.

The contact of the coffee oil with the alcoholic solution of strongmineral acid is preferably carried out with rapid stirring. While thecontact may be carried out at ambient temperatures, the rate ofextraction increases with increase in temperature and the contact ispreferably carried out at reflux.

The duration of the contact may vary depending upon the requirements butpreferably the contact is carried out for a period of time sufficient toremove at least 90% of the cafestol. The duration of the contact mayconveniently be from 15 minutes to 2 hours, but it is preferably from 30to 90 minutes.

The yield is improved by cooling and if the contact has been carried outat an elevated temperature, the mixture is preferably cooled before theoil layer is separated. The mixture may be allowed to cool slowly toroom temperature or even lower and if the contact is carried out atreflux the mixture is preferably allowed to cool over a period of atleast 2 hours before the oil layer is separated.

After the oil layer has been separated it may be washed to remove all orsubstantially all the residual acid with a lower alcohol, convenientlythe same alcohol with which it was contacted, and subsequently dried.Preferably the oil layer is washed with methanol. The separated oil isof a quality comparable to edible vegetable oils and it may be subjectedto further conventional technological treatments. For example it may beprocessed to render it tasteless and to remove traces of methanol bysteam-stripping.

Since the improved oil contains no natural antioxidant, it must beprotected further against organoleptic deterioration due to a highsusceptibility to air oxidation. Therefore, if it is not subjected tothe further processing treatment immediately it should be stabilisedwith antioxidants.

The improved oil may if desired be used for aromatising soluble coffeepowder for example by spraying on to the coffee powder in the form of anemulsion with coffee aroma. Alternatively the improved oil may be usedas an edible vegetable oil.

The following Examples further illustrate the invention.

EXAMPLE 1

One part by weight of coffee oil containing 5.6% by weight of cafestolwas heated under reflux with 10 parts by volume of methanol containing0.1 part by weight of sulphuric acid for 45 minutes and then slowlycooled down to room temperature. After 21/2 hours the oil layer wasremoved, washed three times with 0.5 part of methanol and dried. Theyield was 72% and the amount of cafestol present was found to be 0.20%.

EXAMPLES 2 to 6

A similar procedure to that described in Example 1 was followed but inwhich the amounts of oil and sulphuric acid used, the heating time, theyield and the amount of cafestol found to be present are designated inthe following Table 1.

                  TABLE I                                                         ______________________________________                                               Sulphuric                                                                     acid                                                                          (parts by                                                                              Oil (parts                                                                              Heating       Cafestol                              Example                                                                              weight)  by weight)                                                                              time (mins)                                                                           Yield present                               ______________________________________                                        1      0.1      1.0       45      72%   0.2%                                  2      0.1      0.5       15      68%   0.32%                                 3      0.1      2.0       120     77%   0.40%                                 4      0.05     1.0       120     71%   0.16%                                 5      0.006    1.0       240     74%   0.44%                                 6      0.05     0.5       15      69%   0.16%                                 ______________________________________                                    

EXAMPLES 7 and 8

A similar procedure to that described in Example 1 was followed butinstead of heating at reflux the oil was contacted with the solution ofsulphuric acid in methanol at the temperature and times designated inthe following Table II which also indicates the yield and the amount ofcafestol found to be present.

                  TABLE II                                                        ______________________________________                                        Example                                                                              Temperature                                                                              Time (hours)                                                                             Yield Cafestol present                           ______________________________________                                        7      40° C.                                                                             9         71%   0.32                                       8      26° C.                                                                            15         73%   0.40                                       ______________________________________                                    

I claim:
 1. A process for improving coffee oil consisting essentially ofcontacting coffee oil, under conditions of agitation, with a solution ofa strong mineral acid in a monohydric aliphatic alcohol containing from1 to 3 carbon atoms and then separating the oil layer from the alcohollayer.
 2. A process according to claim 1, wherein the mineral acid usedis sulphuric acid.
 3. A process according to claim 1, wherein theconcentration of mineral acid in the alcohol is from 0.25 to 1.5% on aweight/volume basis.
 4. A process according to claim 1, wherein theproportion of mineral acid to the oil is from 5 to 10 parts by weightper 100 parts by weight of oil.
 5. A process according to claim 1,wherein the alcohol used is methanol.
 6. A process according to claim 1,wherein the concentration of oil in the alcohol is from 7.5 to 12.5parts by weight per 100 parts by volume of alcohol.
 7. A processaccording to claim 1, wherein the coffee oil is contacted with thealcoholic solution of the mineral acid at reflux.